is there a way to make the patterns one single picture on the walls or does it only come in repeated tiles???

You mean like a Mural? If so, then yes. Just not with Create a Pattern. It's something that would have to be done with a program that can actually change the wall itself. The Sims Resource has a program like that called Workshop. I use it often to makes new types of walls and floors. You can check out what people have done at thesimsresource.com

You can also use S3pe, which is another package editor. I have it, but never used it, so I don't know how well it works. But you can download it at http://dino.drealm.info/den/denforum/index.php